<!DOCTYPE html>
<html>
<head>
<style>
body {
  overflow: hidden;
}

button#background {
  position: absolute;
  top: 0;
  left: 0;
  width: 150px;
  height: 40px;
  line-height: 53px;
}

button.clicked {
  background-color: red;
}

button.clicked::after {
  content: " (clicked)";
}

</style>
</head>
<body>
  <button id="background">background</button>
<script>
document.body.addEventListener('click', (e) => {
  e.target.classList.add('clicked');
});
</script>
</body>
</html>
